OUTLINE: Patients undergo percutaneous radiofrequency interstitial tumor ablation (RFA). Patients are offered laparoscopy-assisted percutaneous RFA in the operating room if their tumors are not safely accessible. Intra-operative ultrasound is used to confirm probe placement and to monitor treatment delivery. If the target temperature or impedance are not reached, treatment is repeated no more than twice. No more than 5 tumors are treated per kidney.